I use Stock Diff(4.1) with KAAZ 2 WAY LSD(For Drifting). What speed in 5th gear can I get from 4.3 and 4.7 final gear at 2500, 3000 and 3500 rpm? I have known lower ration make car more responesible. But I wanna find compromised point for me between funny and long trip use(For comfortable).

Nice to meet everyone. And sorry for weak in English.

 

It is just math. Look at the speeds you currently achieve @ a certain rpm level and calculate the percentage change in gear ratio.

 

I don't know for 4.7, but here is something for 3.9, 4.1, 4.3. I hope it helps a little.
http://www.rx7.com/store/rx7/fddrivetrain_rearend.html (scroll to the bottom).

 

Thank you so much that and exactly info that i need.

 

4.3 ... 4.7 is way too low...

 

I bought the 4.3 gears from RP/rx7.com and love them. Really woke the car up in the lower gears

 

by woke up do you mean better acceleration?

 

Yup.

 

You'd light the tires up with an agressive start and lose out on top end speed. I had been thinking about a 4.7 for track use, but theres something about high speed runs that makes me stick to the middle ground 4.1.

 

Which one do yall recommend for faster acceleration and top end speed, just stick wit 4.1?

 

4.1 is a good balance, or 4.3 for some extra poke without a huge loss in top speed. If you decide to do this I'd advise you consider fitting 1.5 way diff which are far tougher than the stock diffs.

3.9 for slower accelaration and much higher top speed (assuming you have a runway to test it).
4.3 increased accelaration and lowered top end - later spec and RZ models used this to increase performance without affecting the top speed to much).
4.7 major increase in accelaration but reduced high speed (unless you fit a 6 speed box with custom ratios to make up for it).

 

The 4.7 would also mean you'd need some serious rubber to put the power down onto the road, as wheelspin would be a problem.

 

Where could one get a 4.7 for the FD diff?

 

You'll probably have to call them on the phone for something like that as its not something they sell regularly, but Rotary Performance in TX and Pettit Racing both use to sell them.

 

Alberto, I wouldn't recommend the 4.7 for a street driven car. Next time you come back to the nyc area you can drive my FD with the 4.3s to see how you like it

 

Definitely not for a street driven car. Just getting ideas for a race car.